1. Field of the Invention
The present invention relates to a zoom lens, and particularly to a zoom lens having a picture angle reaching up to 84 deg. at its wide angle end, and a variable power ratio amounted to about 3, preferably used as an interchangeable lens for a single-lens reflex camera of 35 mm size.
2. Description of the Prior Art
Recently, the picture angle, to be covered, of zoom lenses used as interchangeable lenses for a 35 mm size still camera is more and more large. There may be found two trends in such a kind of zoom lenses.
One of these trends is to increase the variable power ratio of the zoom lens even through the picture angle there of becomes more or less small so that the zoom lens has 28 mm at its wide angle end and a variable power ratio of 3. A zoom lens of this type is disclosed in, for example, Japanese Patent Publication No. 14403/80.
The other of the trends is to provide a zoom lens which has a super-wide angle amounted to 24 mm at its wind angle end even though its variable power ratio is small such as, for example, about 2. Zoom lens of such a kind are disclosed in, for example, Japanese Patent Laid-Open Publication No. 118213/82 and Japanese Patent Laid-Open Publication No. 26816/82.
However, in the former zoom lens, if the zoom lens is shifted to the wide angle side while its zoom ratio is maintained, the amounts of aberrations generated in an obliquely incident light beam, such as, for example, astigmatism and chromatic aberration of magnification in particular, are made large so that a high performance cannot be obtained on the short focal length side, and as well the space between the first and second lens groups becomes large, causing an increase in the diameter of the front lens or a decrease in the brighthess of the edges of the image field.
Meanwhile, in the latter zoom lens, if its zooming range is extended to the telescopic side to increase its zoom ratio, aberration due to an increase in the lens diameter, such as, for example, spherical aberration, color-offset due to spherical aberration, and coma in particular become large. Further, the zoom lens inevitably has a large size since the moving distance of the variator is large, and as well, the operationability of the zoom lens is made deteriorate.